Highly Reliable 4 Mb FeRAM Using a Newly Developed PLZT Capacitor With a Bi-Doped SRO Interlayer

We successfully developed a lanthanum (La)-doped Pb(Zr,Ti)O $_{\boldsymbol {\textbf {3}}}$ (PLZT)-based ferroelectric random access memory (FeRAM) with a newly developed ferroelectric capacitor (FC) employing bismuth (Bi)-doped SrRuO $_{\boldsymbol {\textbf {3}}}$ (B-SRO), aiming to improve the electrical properties and reliability of the FC. Sputter-deposited SrRuO $_{\boldsymbol {\textbf {3}}}$ , commonly used as an interlayer between the metal electrode and ferroelectric layers to improve FC characteristics, does not necessarily result in good electrical properties due to the low atomic density of SRO, typically up to 85%. To address this, we employed a B-SRO interlayer deposited by a B-SRO target with an atomic density up to 95%. FCs utilizing B-SRO exhibit significantly better electrical properties, endurance ( $\gt 10^{\boldsymbol {\textbf {14}}}$ at 90°C), and retention (approximately 10 years at 125°C) compared to FCs without B-SRO. Reliability tests based on JESD22-A108 standards, confirm that our 4Mb FeRAM with B-SRO is highly reliable and commercially available.